/**
 * All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jivesoftware.smackx.bytestreams.socks5;

import java.io.DataInputStream;
import java.io.IOException;

import org.jivesoftware.smack.XMPPException;
import org.jivesoftware.smack.util.StringUtils;

/**
 * A collection of utility methods for SOcKS5 messages.
 * 
 * @author Henning Staib
 */
class Socks5Utils {

	/**
	 * Returns a SHA-1 digest of the given parameters as specified in <a
	 * href="http://xmpp.org/extensions/xep-0065.html#impl-socks5">XEP-0065</a>.
	 * 
	 * @param sessionID
	 *            for the SOCKS5 Bytestream
	 * @param initiatorJID
	 *            JID of the initiator of a SOCKS5 Bytestream
	 * @param targetJID
	 *            JID of the target of a SOCKS5 Bytestream
	 * @return SHA-1 digest of the given parameters
	 */
	public static String createDigest(String sessionID, String initiatorJID,
			String targetJID) {
		StringBuilder b = new StringBuilder();
		b.append(sessionID).append(initiatorJID).append(targetJID);
		return StringUtils.hash(b.toString());
	}

	/**
	 * Reads a SOCKS5 message from the given InputStream. The message can either
	 * be a SOCKS5 request message or a SOCKS5 response message.
	 * <p>
	 * (see <a href="http://tools.ietf.org/html/rfc1928">RFC1928</a>)
	 * 
	 * @param in
	 *            the DataInputStream to read the message from
	 * @return the SOCKS5 message
	 * @throws IOException
	 *             if a network error occurred
	 * @throws XMPPException
	 *             if the SOCKS5 message contains an unsupported address type
	 */
	public static byte[] receiveSocks5Message(DataInputStream in)
			throws IOException, XMPPException {
		byte[] header = new byte[5];
		in.readFully(header, 0, 5);

		if (header[3] != (byte) 0x03) {
			throw new XMPPException("Unsupported SOCKS5 address type");
		}

		int addressLength = header[4];

		byte[] response = new byte[7 + addressLength];
		System.arraycopy(header, 0, response, 0, header.length);

		in.readFully(response, header.length, addressLength + 2);

		return response;
	}

}
